The dynamic range of ion composition analysis instruments is limited by several factors. Two problems are saturation of particle counters and spillover of signals from highly dominant species into channels tuned to minor species.
Instruments designed for composition measurements of hot plasmas in space can suffer greatly from both of these problems because of the wide energy range required and the wide disparity in fluxes encountered in various regions of interest. To detect minor ions in regions of weak fluxes, geometry factors need to be as large as practicable. As a result, in dense plasma regions, problems with saturation by the dominant fluxes and spillover to minor-ion channels become especially acute.
Present-day ion composition instruments have been unable to provide meaningful measurement of minor ion species at the Earth's magnetopause (the boundary between the magnetosphere and the solar wind). This is due to high background levels caused by spillover of dominant proton fluxes. Specifically, this effect has precluded ion composition measurements at energies in the important keV range at the magnetopause.
Previous attempts to solve the dynamic-range problem have involved mechanical constrictions that reduce the throughput equally for all species. This approach alleviates the saturation and spillover problems, but reduces the minor ion throughput to levels that are often undetectable.